Refinement of massive γ phase with enhanced properties in a Ta containing γ-TiAl-based alloys

Ultrafine γ nano-grains and subgrains were successfully obtained through promoting formation of massive γ phase by 0.5 at.% Ta in γ-TiAl-based alloys after rapidly quenching from high-temperature α-phase field. These fine nano-structures were revealed to be three kinds of boundaries: true-twin, antiphase domain and 120° rotational boundaries. The possible refinement mechanism is found to be the reduction of interfacial energies with enrichment of Ta at these boundaries, which is confirmed by first-principle calculation and direct experimental high spatial resolution structure observation. Room temperature nanoindentation test revealed that these nano-structures exhibit enhanced properties compared with those of coarse massive γ phase.